Far-right groups are exploiting the conviction of nine men who were part of a gang that groomed girls for sex to create a "climate of hate" against Muslims, community leaders have warned.

Muslim groups say they have seen an upsurge in hate mail and abusive phone calls since the trial ended this week and community leaders are bracing themselves for more Islamophobic attacks on individual Muslims and mosques across the UK.

"We are already receiving hate mail and hate phone calls even though we issued a very strong statement condemning those involved," said a spokesman for the Muslim Council of Britain. "If it can happen to MCB, you can just imagine what ordinary Muslims are facing as they go about their day-to-day business."

Eight of the nine men convicted at Liverpool crown court for their involvement in a gang in Rochdale, Greater Manchester, that sexually exploited girls were of Pakistani heritage, and Muslim groups say far-right organisations such as the British National party and the English Defence League (EDL) have used the trial to demonise and abuse the entire community.

Fiyaz Mughal, from Faith Matters, which has set up a new helpline to monitor anti-Muslim attacks, said the Islamophobic hatred prompted by the case had added to the "poison" against Muslims.

"This is dangerous for community relations," he said. "There's lots of discussion about 'Muslim paedos', like saying the prophet married a young girl. All of this disgusting talk is adding to the poison against Muslims."

The helpline, Tell Mama, was launched at the same time as the trial began in February and is the UK's first for those wanting to report Islamophobia and record anti-Muslim attacks. About 20% of the cases so far are linked to the EDL, Mughal said, adding: "About half of those cases are online activity where there is invariably a mention of 'Muslim paedos'."

Suleman Nagdi, spokesman for the Leicestershire Federation of Muslim Organisations, who has held talks with EDL representatives in the past, said: "There's a climate of hate in relation to this … We need to tackle the problem, but people within the BNP, the EDL are increasing the rhetoric … It does have an adverse effect within the city … I am sure it will build within the next few weeks."

Security outside Liverpool crown court, where the nine men were tried, was stepped up after hundreds of EDL and BNP protesters picketed the building. The trial was almost derailed when the BNP leader, Nick Griffin, tweeted that seven verdicts had been reached. One of the defendants has now launched an appeal claiming Griffin's tweet showed jury confidentiality was breached. The beginning of the trial was also delayed for a fortnight in February when two Asian defence barristers were attacked outside the courtroom.

The MCB spokesman said Muslims were used to "low-level hatred". "People expect that nowadays, from their fellow travellers on the underground or buses," he said. "That sort of thing happens all the time."

But he said communities were preparing themselves for more serious attacks following the publicity surrounding the grooming trial. "The graffiti on the door of a home, mosques and community centres attacked, a pig's head through the door … it is bound to increase because the racist are waiting for opportunities like this."

The BNP lost every seat it was contesting in last week's local council election and it is now left with just three councillors from a high of 57 three years ago.

In a separate move, the EDL leader Stephen Lennon has announced that he is to become deputy leader of the small British Freedom party, which some analysts fear could replace the BNP as the main far-right party.